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1. Direct Optimal Mapping Image Power Spectrum and its Window Functions

Author

Zhilei Xu, Honggeun Kim, Jacqueline N. Hewitt, Kai-Feng Chen, Nicholas S. Kern, Eleanor Rath, Ruby Byrne, Adélie Gorce, Robert Pascua, Zachary E. Martinot, Joshua S. Dillon, Bryna J. Hazelton, Adrian Liu, Miguel F. Morales, Zara Abdurashidova, Tyrone Adams, James E. Aguirre, Paul Alexander, Zaki S. Ali, Rushelle Baartman, Yanga Balfour, Adam P. Beardsley, Gianni Bernardi, Tashalee S. Billings, Judd D. Bowman, Richard F. Bradley, Philip Bull, Jacob Burba, Steven Carey, Chris L. Carilli, Carina Cheng, David R. DeBoer, Eloy de Lera Acedo, Matt Dexter, Nico Eksteen, John Ely, Aaron Ewall-Wice, Nicolas Fagnoni, Randall Fritz, Steven R. Furlanetto, Kingsley Gale-Sides, Brian Glendenning, Deepthi Gorthi, Bradley Greig, Jasper Grobbelaar, Ziyaad Halday, Jack Hickish, Daniel C. Jacobs, Austin Julius, MacCalvin Kariseb, Joshua Kerrigan, Piyanat Kittiwisit, Saul A. Kohn, Matthew Kolopanis, Adam Lanman, Paul La Plante, Anita Loots, David Harold Edward MacMahon, Lourence Malan, Cresshim Malgas, Keith Malgas, Bradley Marero, Andrei Mesinger, Mathakane Molewa, Tshegofalang Mosiane, Steven G. Murray, Abraham R. Neben, Bojan Nikolic, Hans Nuwegeld, Aaron R. Parsons, Nipanjana Patra, Samantha Pieterse, Nima Razavi-Ghods, James Robnett, Kathryn Rosie, Peter Sims, Craig Smith, Hilton Swarts, Jianrong Tan, Nithyanandan Thyagarajan, Pieter van Wyngaarden, Peter K. G. Williams, Haoxuan Zheng, and HERA Collaboration

Subjects
H I line emission, Radio interferometry, Early universe, Reionization, Astrophysics, QB460-466
Abstract

The key to detecting neutral hydrogen during the epoch of reionization (EoR) is to separate the cosmological signal from the dominating foreground radiation. We developed direct optimal mapping (DOM) to map interferometric visibilities; it contains only linear operations, with full knowledge of point spread functions from visibilities to images. Here, we demonstrate a fast Fourier transform-based image power spectrum and its window functions computed from the DOM images. We use noiseless simulation, based on the Hydrogen Epoch of Reionization Array Phase I configuration, to study the image power spectrum properties. The window functions show

Published
2024
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2. A CHIME/FRB Study of Burst Rate and Morphological Evolution of the Periodically Repeating FRB 20180916B

Author

Ketan R. Sand, Daniela Breitman, Daniele Michilli, Victoria M. Kaspi, Pragya Chawla, Emmanuel Fonseca, Ryan Mckinven, Kenzie Nimmo, Ziggy Pleunis, Kaitlyn Shin, Bridget C. Andersen, Mohit Bhardwaj, P. J. Boyle, Charanjot Brar, Tomas Cassanelli, Amanda M. Cook, Alice P. Curtin, Fengqiu Adam Dong, Gwendolyn M. Eadie, B. M. Gaensler, Jane Kaczmarek, Adam Lanman, Calvin Leung, Kiyoshi W. Masui, Mubdi Rahman, Ayush Pandhi, Aaron B. Pearlman, Emily Petroff, Masoud Rafiei-Ravandi, Paul Scholz, Vishwangi Shah, Kendrick Smith, Ingrid Stairs, and David C. Stenning

Subjects
Radio transient sources, Radio bursts, Astrophysics, QB460-466
Abstract

FRB 20180916B is a repeating fast radio burst (FRB) with a 16.3 day periodicity in its activity. In this study, we present morphological properties of 60 FRB 20180916B bursts detected by CHIME/FRB between 2018 August and 2021 December. We recorded raw voltage data for 45 of these bursts, enabling microseconds time resolution in some cases. We studied variation of spectro-temporal properties with time and activity phase. We find that the variation in dispersion measure (DM) is ≲1 pc cm ^−3 and that there is burst-to-burst variation in scattering time estimates ranging from ∼0.16 to over 2 ms, with no discernible trend with activity phase for either property. Furthermore, we find no DM and scattering variability corresponding to the recent change in rotation measure from the source, which has implications for the immediate environment of the source. We find that FRB 20180916B has thus far shown no epochs of heightened activity as have been seen in other active repeaters by CHIME/FRB, with its burst count consistent with originating from a Poissonian process. We also observe no change in the value of the activity period over the duration of our observations and set a 1 σ upper limit of 1.5 × 10 ^−4 day day ^−1 on the absolute period derivative. Finally, we discuss constraints on progenitor models yielded by our results, noting that our upper limits on changes in scattering and DM as a function of phase do not support models invoking a massive binary companion star as the origin of the 16.3 day periodicity.

Published
2023
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3. Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations

Author

The HERA Collaboration: Zara Abdurashidova, Tyrone Adams, James E. Aguirre, Paul Alexander, Zaki S. Ali, Rushelle Baartman, Yanga Balfour, Rennan Barkana, Adam P. Beardsley, Gianni Bernardi, Tashalee S. Billings, Judd D. Bowman, Richard F. Bradley, Daniela Breitman, Philip Bull, Jacob Burba, Steve Carey, Chris L. Carilli, Carina Cheng, Samir Choudhuri, David R. DeBoer, Eloy de Lera Acedo, Matt Dexter, Joshua S. Dillon, John Ely, Aaron Ewall-Wice, Nicolas Fagnoni, Anastasia Fialkov, Randall Fritz, Steven R. Furlanetto, Kingsley Gale-Sides, Hugh Garsden, Brian Glendenning, Adélie Gorce, Deepthi Gorthi, Bradley Greig, Jasper Grobbelaar, Ziyaad Halday, Bryna J. Hazelton, Stefan Heimersheim, Jacqueline N. Hewitt, Jack Hickish, Daniel C. Jacobs, Austin Julius, Nicholas S. Kern, Joshua Kerrigan, Piyanat Kittiwisit, Saul A. Kohn, Matthew Kolopanis, Adam Lanman, Paul La Plante, David Lewis, Adrian Liu, Anita Loots, Yin-Zhe Ma, David H. E. MacMahon, Lourence Malan, Keith Malgas, Cresshim Malgas, Matthys Maree, Bradley Marero, Zachary E. Martinot, Lisa McBride, Andrei Mesinger, Jordan Mirocha, Mathakane Molewa, Miguel F. Morales, Tshegofalang Mosiane, Julian B. Muñoz, Steven G. Murray, Vighnesh Nagpal, Abraham R. Neben, Bojan Nikolic, Chuneeta D. Nunhokee, Hans Nuwegeld, Aaron R. Parsons, Robert Pascua, Nipanjana Patra, Samantha Pieterse, Yuxiang Qin, Nima Razavi-Ghods, James Robnett, Kathryn Rosie, Mario G. Santos, Peter Sims, Saurabh Singh, Craig Smith, Hilton Swarts, Jianrong Tan, Nithyanandan Thyagarajan, Michael J. Wilensky, Peter K. G. Williams, Pieter van Wyngaarden, and Haoxuan Zheng

Subjects
Astronomy data analysis, Radio interferometers, Intergalactic medium, Reionization, Galaxy formation, Cosmology, Astrophysics, QB460-466
Abstract

We report the most sensitive upper limits to date on the 21 cm epoch of reionization power spectrum using 94 nights of observing with Phase I of the Hydrogen Epoch of Reionization Array (HERA). Using similar analysis techniques as in previously reported limits, we find at 95% confidence that Δ ^2 ( k = 0.34 h Mpc ^−1 ) ≤ 457 mK ^2 at z = 7.9 and that Δ ^2 ( k = 0.36 h Mpc ^−1 ) ≤ 3496 mK ^2 at z = 10.4, an improvement by a factor of 2.1 and 2.6, respectively. These limits are mostly consistent with thermal noise over a wide range of k after our data quality cuts, despite performing a relatively conservative analysis designed to minimize signal loss. Our results are validated with both statistical tests on the data and end-to-end pipeline simulations. We also report updated constraints on the astrophysics of reionization and the cosmic dawn. Using multiple independent modeling and inference techniques previously employed by HERA Collaboration, we find that the intergalactic medium must have been heated above the adiabatic cooling limit at least as early as z = 10.4, ruling out a broad set of so-called “cold reionization” scenarios. If this heating is due to high-mass X-ray binaries during the cosmic dawn, as is generally believed, our result’s 99% credible interval excludes the local relationship between soft X-ray luminosity and star formation and thus requires heating driven by evolved low-metallicity stars.

Published
2023
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4. Effects of model incompleteness on the drift-scan calibration of radio telescopes

Author

Bharat K Gehlot, Daniel C Jacobs, Judd D Bowman, Nivedita Mahesh, Steven G Murray, Matthew Kolopanis, Adam P Beardsley, Zara Abdurashidova, James E Aguirre, Paul Alexander, Zaki S Ali, Yanga Balfour, Gianni Bernardi, Tashalee S Billings, Richard F Bradley, Phil Bull, Jacob Burba, Steve Carey, Chris L Carilli, Carina Cheng, David R DeBoer, Matt Dexter, Eloy de Lera Acedo, Joshua S Dillon, John Ely, Aaron Ewall-Wice, Nicolas Fagnoni, Randall Fritz, Steven R Furlanetto, Kingsley Gale-Sides, Brian Glendenning, Deepthi Gorthi, Bradley Greig, Jasper Grobbelaar, Ziyaad Halday, Bryna J Hazelton, Jacqueline N Hewitt, Jack Hickish, Austin Julius, Nicholas S Kern, Joshua Kerrigan, Piyanat Kittiwisit, Saul A Kohn, Adam Lanman, Paul La Plante, Telalo Lekalake, David Lewis, Adrian Liu, Yin-Zhe Ma, David MacMahon, Lourence Malan, Cresshim Malgas, Matthys Maree, Zachary E Martinot, Eunice Matsetela, Andrei Mesinger, Mathakane Molewa, Raul A Monsalve, Miguel F Morales, Tshegofalang Mosiane, Abraham R Neben, Bojan Nikolic, Aaron R Parsons, Robert Pascua, Nipanjana Patra, Samantha Pieterse, Jonathan C Pober, Nima Razavi-Ghods, Jon Ringuette, James Robnett, Kathryn Rosie, Mario G Santos, Peter Sims, Craig Smith, Angelo Syce, Max Tegmark, Nithyanandan Thyagarajan, Peter K G Williams, and Haoxuan Zheng

Published
2021
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5. Bayesian jackknife tests with a small number of subsets: Application to HERA 21cm power spectrum upper limits

Author

Michael J Wilensky, Fraser Kennedy, Philip Bull, Joshua S Dillon, Zara Abdurashidova, Tyrone Adams, James E Aguirre, Paul Alexander, Zaki S Ali, Rushelle Baartman, Yanga Balfour, Adam P Beardsley, Gianni Bernardi, Tashalee S Billings, Judd D Bowman, Richard F Bradley, Jacob Burba, Steven Carey, Chris L Carilli, Carina Cheng, David R DeBoer, Eloy de Lera Acedo, Matt Dexter, Nico Eksteen, John Ely, Aaron Ewall-Wice, Nicolas Fagnoni, Randall Fritz, Steven R Furlanetto, Kingsley Gale-Sides, Brian Glendenning, Deepthi Gorthi, Bradley Greig, Jasper Grobbelaar, Ziyaad Halday, Bryna J Hazelton, Jacqueline N Hewitt, Jack Hickish, Daniel C Jacobs, Austin Julius, MacCalvin Kariseb, Nicholas S Kern, Joshua Kerrigan, Piyanat Kittiwisit, Saul A Kohn, Matthew Kolopanis, Adam Lanman, Paul La Plante, Adrian Liu, Anita Loots, David Harold Edward MacMahon, Lourence Malan, Cresshim Malgas, Keith Malgas, Bradley Marero, Zachary E Martinot, Andrei Mesinger, Mathakane Molewa, Miguel F Morales, Tshegofalang Mosiane, Steven G Murray, Abraham R Neben, Bojan Nikolic, Hans Nuwegeld, Aaron R Parsons, Nipanjana Patra, Samantha Pieterse, Nima Razavi-Ghods, James Robnett, Kathryn Rosie, Peter Sims, Hilton Swarts, Nithyanandan Thyagarajan, Pieter van Wyngaarden, Peter K G Williams, Haoxuan Zheng, Michael, J Wilensky, Fraser, Kennedy, Philip, Bull, Joshua, S Dillon, Zara, Abdurashidova, Tyrone, Adam, James, E Aguirre, Paul, Alexander, Zaki, S Ali, Rushelle, Baartman, Yanga, Balfour, Adam, P Beardsley, Bernardi, Gianni, Tashalee, S Billing, Judd, D Bowman, Richard, F Bradley, Jacob, Burba, Steven, Carey, Chris, L Carilli, Carina, Cheng, David, R DeBoer, Eloy de Lera Acedo, Matt, Dexter, Nico, Eksteen, John, Ely, Aaron, Ewall-Wice, Nicolas, Fagnoni, Randall, Fritz, Steven, R Furlanetto, Kingsley, Gale-Side, Brian, Glendenning, Deepthi, Gorthi, Greig, Bradley, Jasper, Grobbelaar, Ziyaad, Halday, Bryna, J Hazelton, Jacqueline, N Hewitt, Jack, Hickish, Daniel, C Jacob, Austin, Juliu, Maccalvin, Kariseb, Nicholas, S Kern, Joshua, Kerrigan, Piyanat, Kittiwisit, Saul, A Kohn, Matthew, Kolopani, Adam, Lanman, Paul La Plante, Liu, Adrian Chi-Yan, Anita, Loot, David Harold Edward MacMahon, Lourence, Malan, Cresshim, Malga, Keith, Malga, Bradley, Marero, Zachary, E Martinot, Mesinger, ANDREI ALBERT, Mathakane, Molewa, Miguel, F Morale, Tshegofalang, Mosiane, Steven, G Murray, Abraham, R Neben, Bojan, Nikolic, Hans, Nuwegeld, Aaron, R Parson, Nipanjana, Patra, Samantha, Pieterse, Nima, Razavi-Ghod, James, Robnett, Kathryn, Rosie, Peter, Sim, Hilton, Swart, Thyagarajan, Nithyanandan, Pieter van Wyngaarden, Peter K, G William, and Haoxuan, Zheng

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Settore FIS/05 - Astronomia e Astrofisica, Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We present a Bayesian jackknife test for assessing the probability that a data set contains biased subsets, and, if so, which of the subsets are likely to be biased. The test can be used to assess the presence and likely source of statistical tension between different measurements of the same quantities in an automated manner. Under certain broadly applicable assumptions, the test is analytically tractable. We also provide an open-source code, chiborg, that performs both analytic and numerical computations of the test on general Gaussian-distributed data. After exploring the information theoretical aspects of the test and its performance with an array of simulations, we apply it to data from the Hydrogen Epoch of Reionization Array (HERA) to assess whether different sub-seasons of observing can justifiably be combined to produce a deeper 21 cm power spectrum upper limit. We find that, with a handful of exceptions, the HERA data in question are statistically consistent and this decision is justified. We conclude by pointing out the wide applicability of this test, including to CMB experiments and the H0 tension.

Published
2022

6. Effects of model incompleteness on the drift-scan calibration of radio telescopes

Author

Phil Bull, David DeBoer, Adam P. Beardsley, Nipanjana Patra, Ziyaad Halday, Nima Razavi-Ghods, Nicholas S. Kern, Aaron R. Parsons, Piyanat Kittiwisit, Kingsley Gale-Sides, Robert Pascua, Max Tegmark, Judd D. Bowman, Adam Lanman, Samantha Pieterse, James Robnett, Peter Sims, Gianni Bernardi, Peter K. G. Williams, Miguel F. Morales, Chris Carilli, Saul A. Kohn, Zara Abdurashidova, Eloy de Lera Acedo, Zaki S. Ali, Steven R. Furlanetto, Abraham R. Neben, Eunice Matsetela, Randall Fritz, Bojan Nikolic, Aaron Ewall-Wice, Bryna J. Hazelton, Deepthi Gorthi, Richard F. Bradley, Matthew Kolopanis, Jon Ringuette, Brian Glendenning, Matt Dexter, Joshua S. Dillon, Carina Cheng, Paul La Plante, Austin Julius, S. H. Carey, Nithyanandan Thyagarajan, Haoxuan Zheng, David B. Lewis, Mario G. Santos, Daniel C. Jacobs, Joshua Kerrigan, Steven G. Murray, Cresshim Malgas, Jack Hickish, Adrian Liu, James E. Aguirre, Nicolas Fagnoni, Jacob Burba, Yanga Balfour, Lourence Malan, Craig Smith, Raul A. Monsalve, Bradley Greig, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, Tashalee S. Billings, Zachary E. Martinot, Telalo Lekalake, Matthys Maree, B. K. Gehlot, David MacMahon, Yin-Zhe Ma, Mathakane Molewa, Paul Alexander, Kathryn Rosie, Tshegofalang Mosiane, Nivedita Mahesh, John Ely, Jacqueline N. Hewitt, Angelo Syce, Gehlot, B. K., Jacobs, D. C., Bowman, J. D., Mahesh, N., Murray, S. G., Kolopanis, M., Beardsley, A. P., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Bernardi, G., Billings, T. S., Bradley, R. F., Bull, P., Burba, J., Carey, S., Carilli, C. L., Cheng, C., Deboer, D. R., Dexter, M., De Lera Acedo, E., Dillon, J. S., Ely, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Julius, A., Kern, N. S., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Lanman, A., La Plante, P., Lekalake, T., Lewis, D., Liu, A., Ma, Y. -Z., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Monsalve, R. A., Morales, M. F., Mosiane, T., Neben, A. R., Nikolic, B., Parsons, A. R., Pascua, R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Santos, M. G., Sims, P., Smith, C., Syce, A., Tegmark, M., Thyagarajan, N., Williams, P. K. G., Zheng, H., ITA, and USA

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), 010504 meteorology & atmospheric sciences, media_common.quotation_subject, statistical [methods], FOS: Physical sciences, 01 natural sciences, Radio telescope, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Calibration, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Reionization, 0105 earth and related environmental sciences, Remote sensing, media_common, Physics, COSMIC cancer database, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, interferometric [techniques], interferometer [instrumentation], Interferometry, Amplitude, 13. Climate action, Space and Planetary Science, Sky, data analysi [methods], dark ages, reionization, first star, Antenna (radio), Astrophysics - Instrumentation and Methods for Astrophysics, miscellaneou [instrumentation], Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Precision calibration poses challenges to experiments probing the redshifted 21-cm signal of neutral hydrogen from the Cosmic Dawn and Epoch of Reionization (z~30-6). In both interferometric and global signal experiments, systematic calibration is the leading source of error. Though many aspects of calibration have been studied, the overlap between the two types of instruments has received less attention. We investigate the sky based calibration of total power measurements with a HERA dish and an EDGES style antenna to understand the role of auto-correlations in the calibration of an interferometer and the role of sky in calibrating a total power instrument. Using simulations we study various scenarios such as time variable gain, incomplete sky calibration model, and primary beam model. We find that temporal gain drifts, sky model incompleteness, and beam inaccuracies cause biases in the receiver gain amplitude and the receiver temperature estimates. In some cases, these biases mix spectral structure between beam and sky resulting in spectrally variable gain errors. Applying the calibration method to the HERA and EDGES data, we find good agreement with calibration via the more standard methods. Although instrumental gains are consistent with beam and sky errors similar in scale to those simulated, the receiver temperatures show significant deviations from expected values. While we show that it is possible to partially mitigate biases due to model inaccuracies by incorporating a time-dependent gain model in calibration, the resulting errors on calibration products are larger and more correlated. Completely addressing these biases will require more accurate sky and primary beam models., Comment: 16 pages, 13 figures, 1 table; accepted for publication in MNRAS main journal

Published
2021

7. Characterization Of Inpaint Residuals In Interferometric Measurements of the Epoch Of Reionization

Author

Michael Pagano, Jing Liu, Adrian Liu, Nicholas S Kern, Aaron Ewall-Wice, Philip Bull, Robert Pascua, Siamak Ravanbakhsh, Zara Abdurashidova, Tyrone Adams, James E Aguirre, Paul Alexander, Zaki S Ali, Rushelle Baartman, Yanga Balfour, Adam P Beardsley, Gianni Bernardi, Tashalee S Billings, Judd D Bowman, Richard F Bradley, Jacob Burba, Steven Carey, Chris L Carilli, Carina Cheng, David R DeBoer, Eloy de Lera Acedo, Matt Dexter, Joshua S Dillon, Nico Eksteen, John Ely, Nicolas Fagnoni, Randall Fritz, Steven R Furlanetto, Kingsley Gale-Sides, Brian Glendenning, Deepthi Gorthi, Bradley Greig, Jasper Grobbelaar, Ziyaad Halday, Bryna J Hazelton, Jacqueline N Hewitt, Jack Hickish, Daniel C Jacobs, Austin Julius, MacCalvin Kariseb, Joshua Kerrigan, Piyanat Kittiwisit, Saul A Kohn, Matthew Kolopanis, Adam Lanman, Paul La Plante, Anita Loots, David Harold Edward MacMahon, Lourence Malan, Cresshim Malgas, Keith Malgas, Bradley Marero, Zachary E Martinot, Andrei Mesinger, Mathakane Molewa, Miguel F Morales, Tshegofalang Mosiane, Abraham R Neben, Bojan Nikolic, Hans Nuwegeld, Aaron R Parsons, Nipanjana Patra, Samantha Pieterse, Nima Razavi-Ghods, James Robnett, Kathryn Rosie, Peter Sims, Craig Smith, Hilton Swarts, Nithyanandan Thyagarajan, Pieter van Wyngaarden, Peter K G Williams, and Haoxuan Zheng

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Radio Frequency Interference (RFI) is one of the systematic challenges preventing 21cm interferometric instruments from detecting the Epoch of Reionization. To mitigate the effects of RFI on data analysis pipelines, numerous inpaint techniques have been developed to restore RFI corrupted data. We examine the qualitative and quantitative errors introduced into the visibilities and power spectrum due to inpainting. We perform our analysis on simulated data as well as real data from the Hydrogen Epoch of Reionization Array (HERA) Phase 1 upper limits. We also introduce a convolutional neural network that capable of inpainting RFI corrupted data in interferometric instruments. We train our network on simulated data and show that our network is capable at inpainting real data without requiring to be retrained. We find that techniques that incorporate high wavenumbers in delay space in their modeling are best suited for inpainting over narrowband RFI. We also show that with our fiducial parameters Discrete Prolate Spheroidal Sequences (DPSS) and CLEAN provide the best performance for intermittent ``narrowband'' RFI while Gaussian Progress Regression (GPR) and Least Squares Spectral Analysis (LSSA) provide the best performance for larger RFI gaps. However we caution that these qualitative conclusions are sensitive to the chosen hyperparameters of each inpainting technique. We find these results to be consistent in both simulated and real visibilities. We show that all inpainting techniques reliably reproduce foreground dominated modes in the power spectrum. Since the inpainting techniques should not be capable of reproducing noise realizations, we find that the largest errors occur in the noise dominated delay modes. We show that in the future, as the noise level of the data comes down, CLEAN and DPSS are most capable of reproducing the fine frequency structure in the visibilities of HERA data., Comment: 21 pages, 13 figures

Published
2022
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8. Validation Solutions to the Full-Sky Radio Interferometry Measurement Equation for Diffuse Emission

Author

Daniel Jacobs, Steven Murray, and Adam Lanman

Subjects
Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics
Abstract

Low-frequency radio observatories are reaching unprecedented levels of sensitivity in an effort to detect the 21 cm signal from the Cosmic Dawn. High precision is needed because the expected signal is overwhelmed by foreground contamination, largely from so-called diffuse emission -- a non-localized glow comprising Galactic synchrotron emission and radio galaxies. The impact of this diffuse emission on observations may be better understood through detailed simulations, which evaluate the Radio Interferometry Measurement Equation (RIME) for a given instrument and sky model. Evaluating the RIME involves carrying out an integral over the full sky, which is naturally discretized for point sources but must be approximated for diffuse emission. The choice of integration scheme can introduce errors that must be understood and isolated from the instrumental effects under study. In this paper, we present several analytically-defined patterns of unpolarized diffuse sky emission for which the RIME integral is manageable, yielding closed-form or series visibility functions. We demonstrate the usefulness of these RIME solutions for validation by comparing them to simulated data, and show that the remaining differences behave as expected with varied sky resolution and baseline orientation and length., 28 pages, 13 figures

Published
2021

9. Automated Detection of Antenna Malfunctions in Large-N Interferometers: A Case Study with the Hydrogen Epoch of Reionization Array

Author

Dara Storer, Joshua S. Dillon, Daniel C. Jacobs, Miguel F. Morales, Bryna J. Hazelton, Aaron Ewall‐Wice, Zara Abdurashidova, James E. Aguirre, Paul Alexander, Zaki S. Ali, Yanga Balfour, Adam P. Beardsley, Gianni Bernardi, Tashalee S. Billings, Judd D. Bowman, Richard F. Bradley, Philip Bull, Jacob Burba, Steven Carey, Chris L. Carilli, Carina Cheng, David R. DeBoer, Eloy Lera Acedo, Matt Dexter, Scott Dynes, John Ely, Nicolas Fagnoni, Randall Fritz, Steven R. Furlanetto, Kingsley Gale‐Sides, Brian Glendenning, Deepthi Gorthi, Bradley Greig, Jasper Grobbelaar, Ziyaad Halday, Jacqueline N. Hewitt, Jack Hickish, Tian Huang, Alec Josaitis, Austin Julius, MacCalvin Kariseb, Nicholas S. Kern, Joshua Kerrigan, Piyanat Kittiwisit, Saul A. Kohn, Matthew Kolopanis, Adam Lanman, Paul La Plante, Adrian Liu, Anita Loots, David MacMahon, Lourence Malan, Cresshim Malgas, Zachary E. Martinot, Andrei Mesinger, Mathakane Molewa, Tshegofalang Mosiane, Steven G. Murray, Abraham R. Neben, Bojan Nikolic, Chuneeta Devi Nunhokee, Aaron R. Parsons, Robert Pascua, Nipanjana Patra, Samantha Pieterse, Jonathan C. Pober, Nima Razavi‐Ghods, Daniel Riley, James Robnett, Kathryn Rosie, Mario G. Santos, Peter Sims, Saurabh Singh, Craig Smith, Jianrong Tan, Nithyanandan Thyagarajan, Peter K. G. Williams, Haoxuan Zheng, Storer, D., Dillon, J. S., Jacobs, D. C., Morales, M. F., Hazelton, B. J., Ewall-Wice, A., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Bernardi, G., Billings, T. S., Bowman, J. D., Bradley, R. F., Bull, P., Burba, J., Carey, S., Carilli, C. L., Cheng, C., Deboer, D. R., de Lera Acedo, E., Dexter, M., Dynes, S., Ely, J., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hewitt, J. N., Hickish, J., Huang, T., Josaitis, A., Julius, A., Kariseb, M., Kern, N. S., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., La Plante, P., Liu, A., Loots, A., Macmahon, D., Malan, L., Malgas, C., Martinot, Z. E., Mesinger, A., Molewa, M., Mosiane, T., Murray, S. G., Neben, A. R., Nikolic, B., Nunhokee, C. D., Parsons, A. R., Pascua, R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Riley, D., Robnett, J., Rosie, K., Santos, M. G., Sims, P., Singh, S., Smith, C., Tan, J., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), 010308 nuclear & particles physics, FOS: Physical sciences, interferometry, Condensed Matter Physics, 01 natural sciences, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, radio cosmology, reionization, General Earth and Planetary Sciences, flagging, Electrical and Electronic Engineering, Astrophysics - Instrumentation and Methods for Astrophysics, systematics, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We present a framework for identifying and flagging malfunctioning antennas in large radio interferometers. We outline two distinct categories of metrics designed to detect outliers along known failure modes of large arrays: cross-correlation metrics, based on all antenna pairs, and auto-correlation metrics, based solely on individual antennas. We define and motivate the statistical framework for all metrics used, and present tailored visualizations that aid us in clearly identifying new and existing systematics. We implement these techniques using data from 105 antennas in the Hydrogen Epoch of Reionization Array (HERA) as a case study. Finally, we provide a detailed algorithm for implementing these metrics as flagging tools on real data sets., Comment: 31 pages, 17 figures

Published
2021

10. Methods of Error Estimation for Delay Power Spectra in $21\,\textrm{cm}$ Cosmology

Author

David MacMahon, Zara Abdurashidova, Bryna J. Hazelton, David DeBoer, Austin Julius, Jon Ringuette, Jacqueline N. Hewitt, Joshua Kerrigan, Adam Lanman, Jack Hickish, Richard F. Bradley, Matthew Kolopanis, Mathakane Molewa, Angelo Syce, Aaron Ewall-Wice, Jacob Burba, Kathryn Rosie, Daniel C. Jacobs, Judd D. Bowman, Samantha Pieterse, Tshegofalang Mosiane, Cresshim Malgas, Nicolas Fagnoni, James E. Aguirre, Yanga Balfour, Lourence Malan, Paul Alexander, Brian Glendenning, Carina Cheng, Deepthi Gorthi, Nithyanandan Thyagarajan, Joshua S. Dillon, Telalo Lekalake, Jonathan C. Pober, Steve R. Furlanetto, John Ely, Matt Dexter, Andrei Mesinger, Jasper Grobbelaar, Steven Carey, Haoxuan Zheng, Gianni Bernardi, Bradley Greig, Peter Sims, Chuneeta D. Nunhokee, Miguel F. Morales, Craig Smith, Chris Carilli, Matthys Maree, Eloy de Lera Acedo, Tashalee S. Billings, Zachary E. Martinot, Zaki S. Ali, Jianrong Tan, Eunice Matsetela, Adrian Liu, Philip Bull, Bojan Nikolic, Paul La Plante, Peter K. G. Williams, Nima Razavi-Ghods, James Robnett, Nicholas S. Kern, Abraham R. Neben, Randall Fritz, Aaron R. Parsons, Adam P. Beardsley, Saul A. Kohn, Saurabh Singh, Steven G. Murray, Piyanat Kittiwisit, Kingsley Gale-Sides, Nipanjana Patra, Ziyaad Halday, Tan, J., Liu, A., Kern, N. S., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Bernardi, G., Billings, T. S., Bowman, J. D., Bradley, R. F., Bull, P., Burba, J., Carey, S., Carilli, C. L., Cheng, C., Deboer, D. R., Dexter, M., De Lera Acedo, E., Dillon, J. S., Ely, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Julius, A., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., La Plante, P., Lekalake, T., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Murray, S. G., Neben, A. R., Nikolic, B., Nunhokee, C. D., Parsons, A. R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sims, P., Singh, S., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
Physics, Noise power, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Spectral density, FOS: Physical sciences, Astronomy and Astrophysics, Probability density function, 06 humanities and the arts, HERA, 0603 philosophy, ethics and religion, 01 natural sciences, Signal, Power (physics), Settore FIS/05 - Astronomia e Astrofisica, Space and Planetary Science, 060302 philosophy, 0103 physical sciences, Limit (mathematics), Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Reionization, Algorithm, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Precise measurements of the 21 cm power spectrum are crucial for understanding the physical processes of hydrogen reionization. Currently, this probe is being pursued by low-frequency radio interferometer arrays. As these experiments come closer to making a first detection of the signal, error estimation will play an increasingly important role in setting robust measurements. Using the delay power spectrum approach, we have produced a critical examination of different ways that one can estimate error bars on the power spectrum. We do this through a synthesis of analytic work, simulations of toy models, and tests on small amounts of real data. We find that, although computed independently, the different error bar methodologies are in good agreement with each other in the noise-dominated regime of the power spectrum. For our preferred methodology, the predicted probability distribution function is consistent with the empirical noise power distributions from both simulated and real data. This diagnosis is mainly in support of the forthcoming HERA upper limit, and also is expected to be more generally applicable., Comment: 35 Pages, 9 Figures, 4 Tables. Replaced with accepted ApJ version; some clarifying text added in response to referee comments with no changes to results

Published
2021
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11. A Real Time Processing System for Big Data in Astronomy: Applications to HERA

Author

Aaron Ewall-Wice, Daniel C. Jacobs, Craig Smith, Cresshim Malgas, Nicolas Fagnoni, Nipanjana Patra, James Robnett, Lourence Malan, Yanga Balfour, Joshua Kerrigan, Ziyaad Halday, Steve R. Furlanetto, M. Wilensky, Peter Sims, Paul Alexander, Judd D. Bowman, Samantha Pieterse, Nima Razavi-Ghods, Piyanat Kittiwisit, Angelo Syce, Richard F. Bradley, Matthew Kolopanis, Peter K. G. Williams, Jonathan C. Pober, Telalo Lekalake, Andrei Mesinger, Jasper Grobbelaar, Brian Glendenning, D. R. DeBoer, Kingsley Gale-Sides, John Ely, Gianni Bernardi, Tashalee S. Billings, Zachary E. Martinot, Mario G. Santos, Carina Cheng, Matthys Maree, Miguel F. Morales, Adrian Liu, Kathryn Rosie, Robert Pascua, Nithyanandan Thyagarajan, Zaki S. Ali, Nicholas S. Kern, Bryna J. Hazelton, Bojan Nikolic, Zara Abdurashidova, Jacqueline N. Hewitt, Chris Carilli, Austin Julius, P. La Plante, S. Murray, Mathakane Molewa, Bradley Greig, David B. Lewis, Tshegofalang Mosiane, Adam Lanman, Deepthi Gorthi, Joshua S. Dillon, Haoxuan Zheng, Eunice Matsetela, James E. Aguirre, Dave MacMahon, S. H. Carey, E. de Lera Acedo, Aaron R. Parsons, Matthew R. Dexter, Jon Ringuette, Abraham R. Neben, Randall Fritz, Jack Hickish, Jacob Burba, Adam P. Beardsley, Saul A. Kohn, Philip Bull, La Plante, P., Williams, P. K. G., Kolopanis, M., Dillon, J. S., Beardsley, A. P., Kern, N. S., Wilensky, M., Ali, Z. S., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Balfour, Y., Bernardi, G., Billings, T. S., Bowman, J. D., Bradley, R. F., Bull, P., Burba, J., Carey, S., Carilli, C. L., Cheng, C., Deboer, D. R., Dexter, M., de Lera Acedo, E., Ely, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Julius, A., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Lanman, A., Lekalake, T., Lewis, D., Liu, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Murray, S., Neben, A. R., Nikolic, B., Parsons, A. R., Pascua, R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Santos, M. G., Sims, P., Smith, C., Syce, A., Thyagarajan, N., Zheng, H., ITA, and USA

Subjects
Data analysis — Software, Astronomy — Software, Computer science, Real-time computing, Big data, FOS: Physical sciences, 0102 computer and information sciences, Development, Terabyte, Interference (wave propagation), 7. Clean energy, 01 natural sciences, Computer Science::Digital Libraries, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Methods, 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), business.industry, SIGNAL (programming language), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, HERA, Computer Science Applications, 010201 computation theory & mathematics, Space and Planetary Science, Computer data storage, Data analysis — Physical sciences and engineering, Astrophysics - Instrumentation and Methods for Astrophysics, business, Raw data
Abstract

As current- and next-generation astronomical instruments come online, they will generate an unprecedented deluge of data. Analyzing these data in real time presents unique conceptual and computational challenges, and their long-term storage and archiving is scientifically essential for generating reliable, reproducible results. We present here the real-time processing (RTP) system for the Hydrogen Epoch of Reionization Array (HERA), a radio interferometer endeavoring to provide the first detection of the highly redshifted 21 cm signal from Cosmic Dawn and the Epoch of Reionization by an interferometer. The RTP system consists of analysis routines run on raw data shortly after they are acquired, such as calibration and detection of radio-frequency interference (RFI) events. RTP works closely with the Librarian, the HERA data storage and transfer manager which automatically ingests data and transfers copies to other clusters for post-processing analysis. Both the RTP system and the Librarian are public and open source software, which allows for them to be modified for use in other scientific collaborations. When fully constructed, HERA is projected to generate over 50 terabytes (TB) of data each night, and the RTP system enables the successful scientific analysis of these data., Comment: 15 pages, 3 figures, published in Astronomy and Computing

Published
2021
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12. Redundant-baseline calibration of the hydrogen epoch of reionization array

Author

Adrian Liu, Craig Smith, Paul Alexander, John Ely, Deepthi Gorthi, Nithyanandan Thyagarajan, Steven G. Murray, Joshua S. Dillon, Bryna J. Hazelton, Phil Bull, Nipanjana Patra, Jon Ringuette, Zara Abdurashidova, Ziyaad Halday, Aaron R. Parsons, Bradley Greig, Lourence Malan, Angelo Syce, Gianni Bernardi, Piyanat Kittiwisit, Austin Julius, Daniel C. Jacobs, Kingsley Gale-Sides, Jack Hickish, Yin-Zhe Ma, Jonathan C. Pober, Kathryn Rosie, Adam P. Beardsley, Robert Pascua, Peter K. G. Williams, Cresshim Malgas, S. H. Carey, Jacob Burba, Nicolas Fagnoni, David MacMahon, Andrei Mesinger, Jasper Grobbelaar, Yanga Balfour, Joshua Kerrigan, Max Tegmark, Richard F. Bradley, Matthew Kolopanis, David DeBoer, Abraham R. Neben, Mario G. Santos, Randall Fritz, Jacqueline N. Hewitt, Tashalee S. Billings, Zachary E. Martinot, Eunice Matsetela, Saul A. Kohn, David Lewis, Peter Sims, Mathakane Molewa, Naomi Orosz, Steven R. Furlanetto, Paul La Plante, Chuneeta D. Nunhokee, Matt Dexter, Tshegofalang Mosiane, Nicholas S. Kern, Judd D. Bowman, Samantha Pieterse, Max E. Lee, James E. Aguirre, Nima Razavi-Ghods, Miguel F. Morales, Zaki S. Ali, Bojan Nikolic, Aaron Ewall-Wice, Chris Carilli, Eloy de Lera Acedo, James Robnett, Brian Glendenning, Carina Cheng, Matthys Maree, Telalo Lekalake, Haoxuan Zheng, Adam Lanman, ITA, USA, ZAF, Dillon, J. S., Lee, M., Ali, Z. S., Parsons, A. R., Orosz, N., Nunhokee, C. D., La Plante, P., Beardsley, A. P., Kern, N. S., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Balfour, Y., Bernardi, G., Billings, T. S., Bowman, J. D., Bradley, R. F., Bull, P., Burba, J., Carey, S., Carilli, C. L., Cheng, C., Deboer, D. R., Dexter, M., de Lera Acedo, E., Ely, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Julius, A., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., Lekalake, T., Lewis, D., Liu, A., Ma, Y. -Z., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Murray, S., Neben, A. R., Nikolic, B., Pascua, R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Santos, M. G., Sims, P., Smith, C., Syce, A., Tegmark, M., Thyagarajan, N., Williams, P. K. G., Zheng, H., Alexander, Paul [0000-0002-0292-9513], De Lera Acedo, Eloy [0000-0001-8530-6989], Nikolic, Bojan [0000-0001-7168-2705], Razavi-Ghods, Nima [0000-0003-2930-5396], and Apollo - University of Cambridge Repository

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Calibration (statistics), interferometers [instrumentation], first stars, Degrees of freedom (statistics), FOS: Physical sciences, Astronomy & Astrophysics, 01 natural sciences, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Astronomical interferometer, dark ages, reionization, first stars, dark ages, instrumentation: interferometers, 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, 010308 nuclear & particles physics, Noise (signal processing), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, HERA, Interferometry, Dark ages, reionization, first star, Space and Planetary Science, astro-ph.CO, reionization, Antenna (radio), Astrophysics - Instrumentation and Methods for Astrophysics, Algorithm, Astronomical and Space Sciences, Astrophysics - Cosmology and Nongalactic Astrophysics, astro-ph.IM
Abstract

In 21 cm cosmology, precision calibration is key to the separation of the neutral hydrogen signal from very bright but spectrally-smooth astrophysical foregrounds. The Hydrogen Epoch of Reionization Array (HERA), an interferometer specialized for 21 cm cosmology and now under construction in South Africa, was designed to be largely calibrated using the self-consistency of repeated measurements of the same interferometric modes. This technique, known as "redundant-baseline calibration" resolves most of the internal degrees of freedom in the calibration problem. It assumes, however, on antenna elements with identical primary beams placed precisely on a redundant grid. In this work, we review the detailed implementation of the algorithms enabling redundant-baseline calibration and report results with HERA data. We quantify the effects of real-world non-redundancy and how they compare to the idealized scenario in which redundant measurements differ only in their noise realizations. Finally, we study how non-redundancy can produce spurious temporal structure in our calibration solutions--both in data and in simulations--and present strategies for mitigating that structure., Comment: 24 Pages, 19 Figures. Updated to match the accepted MNRAS version

Published
2020

13. DAYENU: A Simple Filter of Smooth Foregrounds for Intensity Mapping Power Spectra

Author

Adrian Liu, Joshua S. Dillon, Aaron R. Parsons, Adam Lanman, T. Joseph W. Lazio, Philip Bull, Tzu-Ching Chang, James E. Aguirre, Chuneeta D. Nunhokee, Saurabh Singh, Aaron Ewall-Wice, Paul La Plante, Eloy de Lera Acedo, David DeBoer, Nicolas Fagnoni, Nicholas S. Kern, and Sean Weinberg

Subjects
Physics, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Basis (linear algebra), 010308 nuclear & particles physics, Intensity mapping, Estimator, FOS: Physical sciences, Astronomy and Astrophysics, Filter (signal processing), 01 natural sciences, Weighting, symbols.namesake, Matrix (mathematics), Fourier transform, Space and Planetary Science, Frequency domain, 0103 physical sciences, symbols, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Algorithm, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We introduce DAYENU, a linear, spectral filter for HI intensity mapping that achieves the desirable foreground mitigation and error minimization properties of inverse co-variance weighting with minimal modeling of the underlying data. Beyond 21 cm power-spectrum estimation, our filter is suitable for any analysis where high dynamic-range removal of spectrally smooth foregrounds in irregularly (or regularly) sampled data is required, something required by many other intensity mapping techniques. Our filtering matrix is diagonalized by Discrete Prolate Spheroidal Sequences which are an optimal basis to model band-limited foregrounds in 21 cm intensity mapping experiments in the sense that they maximally concentrate power within a finite region of Fourier space. We show that DAYENU enables the access of large-scale line-of-sight modes that are inaccessible to tapered DFT estimators. Since these modes have the largest SNRs, DAYENU significantly increases the sensitivity of 21 cm analyses over tapered Fourier transforms. Slight modifications allow us to use DAYENU as a linear replacement for iterative delay CLEANing (DAYENUREST). We refer readers to the Code section at the end of this paper for links to examples and code., Accepted to MNRAS, 19 pages, 17 figures. Replacement matches accepted version

Published
2020

14. Detection of cosmic structures using the bispectrum phase. II. First results from application to cosmic reionization using the Hydrogen Epoch of Reionization Array

Author

Kathryn Rosie, James E. Aguirre, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, David MacMahon, Nipanjana Patra, Tashalee S. Billings, Zachary E. Martinot, Ziyaad Halday, Deepthi Gorthi, Joshua S. Dillon, S. H. Carey, Paul Alexander, Haoxuan Zheng, Eunice Matsetela, Piyanat Kittiwisit, Adam P. Beardsley, Saul A. Kohn, Jon Ringuette, Kingsley Gale-Sides, Joshua Kerrigan, John Ely, Siyanda Matika, Zara Abdurashidova, David DeBoer, Nithyanandan Thyagarajan, Aaron R. Parsons, Matt Dexter, Bryna J. Hazelton, Adrian Liu, Nicholas S. Kern, James Kent, Jack Hickish, Judd D. Bowman, Samantha Pieterse, James Robnett, Miguel F. Morales, Paul La Plante, Richard F. Bradley, Matthew Kolopanis, Austin Julius, Chris Carilli, Eloy de Lera Acedo, Peter K. G. Williams, Craig Smith, Jacob Burba, Zaki S. Ali, Brian Glendenning, Jacqueline N. Hewitt, Carina Cheng, Gianni Bernardi, David B. Lewis, Bojan Nikolic, Aaron Ewall-Wice, Abraham R. Neben, Randall Fritz, Steven R. Furlanetto, Mathakane Molewa, Tshegofalang Mosiane, Lourence Malan, Bradley Greig, Nima Razavi-Ghods, Adam Lanman, Peter Sims, Daniel C. Jacobs, Cresshim Malgas, Nicolas Fagnoni, Yanga Balfour, Angelo Syce, Telalo Lekalake, Matthys Maree, Thyagarajan, N., Carilli, C. L., Nikolic, B., Kent, J., Mesinger, A., Kern, N. S., Bernardi, G., Matika, S., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Billings, T. S., Bowman, J. D., Bradley, R. F., Burba, J., Carey, S., Cheng, C., Deboer, D. R., Dexter, M., Acedo, E. D. L., Dillon, J. S., Ely, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Julius, A., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., La Plante, P., Lekalake, T., Lewis, D., Liu, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Molewa, M., Morales, M. F., Mosiane, T., Neben, A. R., Parsons, A. R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sims, P., Smith, C., Syce, A., Williams, P. K. G., Zheng, H., Nikolic, Bojan [0000-0001-7168-2705], Kent, James [0000-0003-3331-2409], Alexander, Paul [0000-0002-0292-9513], Razavi-Ghods, Nima [0000-0003-2930-5396], Apollo - University of Cambridge Repository, ITA, USA, and ZAF

Subjects
Brightness, Cosmology and Nongalactic Astrophysics (astro-ph.CO), FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Atomic, 01 natural sciences, Cosmology, Radio telescope, Particle and Plasma Physics, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Nuclear, Astrophysics - Cosmology and Nongalactic Astrophysic, 010306 general physics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Reionization, Physics, Quantum Physics, COSMIC cancer database, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Molecular, Nuclear & Particles Physics, Redshift, 5101 Astronomical Sciences, astro-ph.CO, Hydrogen line, Astrophysics - Instrumentation and Methods for Astrophysics, 51 Physical Sciences, Bispectrum, Astronomical and Space Sciences, astro-ph.IM, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Characterizing the epoch of reionization (EoR) at $z\gtrsim 6$ via the redshifted 21 cm line of neutral Hydrogen (HI) is critical to modern astrophysics and cosmology, and thus a key science goal of many current and planned low-frequency radio telescopes. The primary challenge to detecting this signal is the overwhelmingly bright foreground emission at these frequencies, placing stringent requirements on the knowledge of the instruments and inaccuracies in analyses. Results from these experiments have largely been limited not by thermal sensitivity but by systematics, particularly caused by the inability to calibrate the instrument to high accuracy. The interferometric bispectrum phase is immune to antenna-based calibration and errors therein, and presents an independent alternative to detect the EoR HI fluctuations while largely avoiding calibration systematics. Here, we provide a demonstration of this technique on a subset of data from the Hydrogen Epoch of Reionization Array (HERA) to place approximate constraints on the brightness temperature of the intergalactic medium (IGM). From this limited data, at $z=7.7$ we infer "$1\sigma$" upper limits on the IGM brightness temperature to be $\le 316$ "pseudo" mK at $\kappa_\parallel=0.33$ "pseudo" $h$ Mpc$^{-1}$ (data-limited) and $\le 1000$ "pseudo" mK at $\kappa_\parallel=0.875$ "pseudo" $h$ Mpc$^{-1}$ (noise-limited). The "pseudo" units denote only an approximate and not an exact correspondence to the actual distance scales and brightness temperatures. By propagating models in parallel to the data analysis, we confirm that the dynamic range required to separate the cosmic HI signal from the foregrounds is similar to that in standard approaches, and the power spectrum of the bispectrum phase is still data-limited (at $\gtrsim 10^6$ dynamic range) indicating scope for further improvement in sensitivity as the array build-out continues., Comment: 22 pages, 12 figures (including sub-figures). Published in PhRvD. Abstract may be slightly abridged compared to the actual manuscript due to length limitations on arXiv

Published
2020

15. The impact of tandem redundant/sky-based calibration in MWA Phase II data analysis

Author

Nichole Barry, Adam Lanman, Wenyang Li, Q. Zheng, M. Wilensky, Randall B. Wayth, Kenji Hasegawa, Daniel A. Mitchell, Christopher H. Jordan, Rachel L. Webster, Jonathan C. Pober, R. Byrne, Cathryn M. Trott, Steven Tingay, Miguel F. Morales, M. Rahimi, Bryna J. Hazelton, J. L. B. Line, Daniel C. Jacobs, Zheng Zhang, A. Chokshi, Steven G. Murray, Keitaro Takahashi, Shintaro Yoshiura, Christene Lynch, R. C. Joseph, B. Pindor, Benjamin McKinley, and Adam P. Beardsley

Subjects
Physics, 010308 nuclear & particles physics, Radio galaxy, Calibration (statistics), media_common.quotation_subject, Instrumentation, FOS: Physical sciences, Spectral density, Astronomy and Astrophysics, Murchison Widefield Array, 01 natural sciences, Space and Planetary Science, Sky, 0103 physical sciences, Astronomical interferometer, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Reionization, Remote sensing, media_common
Abstract

Precise instrumental calibration is of crucial importance to 21-cm cosmology experiments. The Murchison Widefield Array's (MWA) Phase II compact configuration offers us opportunities for both redundant calibration and sky-based calibration algorithms; using the two in tandem is a potential approach to mitigate calibration errors caused by inaccurate sky models. The MWA Epoch of Reionization (EoR) experiment targets three patches of the sky (dubbed EoR0, EoR1, and EoR2) with deep observations. Previous work in \cite{Li_2018} and \cite{Wenyang_2019} studied the effect of tandem calibration on the EoR0 field and found that it yielded no significant improvement in the power spectrum over sky-based calibration alone. In this work, we apply similar techniques to the EoR1 field and find a distinct result: the improvements in the power spectrum from tandem calibration are significant. To understand this result, we analyze both the calibration solutions themselves and the effects on the power spectrum over three nights of EoR1 observations. We conclude that the presence of the bright radio galaxy Fornax A in EoR1 degrades the performance of sky-based calibration, which in turn enables redundant calibration to have a larger impact. These results suggest that redundant calibration can indeed mitigate some level of model-incompleteness error., Comment: 20 pages, 11 figures, accepted for publication in PASA

Published
2020

16. Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array

Author

Juan Mena Parra, Piyanat Kittiwisit, Kingsley Gale-Sides, Joshua Kerrigan, Honggeun Kim, Adrian Liu, Phil Bull, Nipanjana Patra, Ziyaad Halday, Matthys Maree, James E. Aguirre, Bryna J. Hazelton, Jacqueline N. Hewitt, Zara Abdurashidova, Saul A. Kohn, Judd D. Bowman, Matt Dexter, K. Gale-Sides, Samantha Pieterse, Paul La Plante, Mathakane Molewa, James Kent, Nithyanandan Thyagarajan, Eunice Matsetela, Nicolas Fagnoni, Adam P. Beardsley, Alec Josaitis, Kathryn Rosie, David MacMahon, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, Tashalee S. Billings, Zachary E. Martinot, Tshegofalang Mosiane, Abraham R. Neben, Austin Julius, Randall Fritz, Siyanda Matika, Brian Glendenning, Carina Cheng, Peter Sims, Paul Alexander, Daniel C. Jacobs, Steve R. Furlanetto, Gianni Bernardi, Bradley Greig, Lourence Malan, Nima Razavi-Ghods, Cresshim Malgas, Yanga Balfour, Nicholas S. Kern, Telalo Lekalake, David DeBoer, Aaron R. Parsons, Richard F. Bradley, Matthew Kolopanis, Deepthi Gorthi, Peter K. G. Williams, James Robnett, Joshua S. Dillon, Chris Carilli, Eloy de Lera Acedo, Miguel F. Morales, Zaki S. Ali, Bojan Nikolic, Aaron Ewall-Wice, Jack Hickish, Jacob Burba, Angelo Syce, Haoxuan Zheng, Adam Lanman, ITA, USA, ZAF, Carilli, C. L., Thyagarajan, N., Kent, J., Nikolic, B., Gale-Sides, K., Kern, N. S., Bernardi, G., Mesinger, A., Matika, S., Abdurashidova, Zara, Aguirre, James E., Paul, Alexander Christian, Ali, Zaki S., Balfour, Yanga, Beardsley, Adam P., Billings, Tashalee S., Bowman, Judd D., Bradley, Richard F., Bull, Phil, Burba, Jacob, Cheng, Carina, Deboer, David R., Dexter, Matt, Acedo, Eloy de Lera, Dillon, Joshua S., Ewall-Wice, Aaron, Fagnoni, Nicola, Fritz, Randall, Furlanetto, Steve R., Gale-Sides, Kingsley, Glendenning, Brian, Gorthi, Deepthi, Greig, Bradley, Grobbelaar, Jasper, Halday, Ziyaad, Hazelton, Bryna J., Hewitt, Jacqueline N., Hickish, Jack, Jacobs, Daniel C., Josaitis, Alec, Julius, Austin, Kerrigan, Joshua, Kim, Honggeun, Kittiwisit, Piyanat, Kohn, Saul A., Kolopanis, Matthew, Lanman, Adam, Plante, Paul La, Lekalake, Telalo, Liu, Adrian, Macmahon, David, Malan, Lourence, Malgas, Cresshim, Maree, Matthy, Martinot, Zachary E., Matsetela, Eunice, Molewa, Mathakane, Morales, Miguel F., Mosiane, Tshegofalang, Neben, Abraham R., Parra, Juan Mena, Parsons, Aaron R., Patra, Nipanjana, Pieterse, Samantha, Pober, Jonathan C., Razavi-Ghods, Nima, Robnett, Jame, Rosie, Kathryn, Sims, Peter, Syce, Angelo, Williams, Peter K. G., Zheng, Haoxuan, Carilli, CL [0000-0001-6647-3861], Thyagarajan, N [0000-0003-1602-7868], Kern, NS [0000-0002-8211-1892], Bernardi, G [0000-0002-0916-7443], Aguirre, JE [0000-0002-4810-666X], Beardsley, AP [0000-0001-9428-8233], Bowman, JD [0000-0002-8475-2036], Bull, P [0000-0001-5668-3101], Dillon, JS [0000-0003-3336-9958], Ewall-Wice, A [0000-0002-0086-7363], Furlanetto, SR [0000-0002-0658-1243], Hazelton, BJ [0000-0001-7532-645X], Jacobs, DC [0000-0002-0917-2269], Kerrigan, J [0000-0002-1876-272X], Kittiwisit, P [0000-0003-0953-313X], Kohn, SA [0000-0001-6744-5328], Kolopanis, M [0000-0002-2950-2974], Liu, A [0000-0001-6876-0928], Morales, MF [0000-0001-7694-4030], Neben, AR [0000-0001-7776-7240], Patra, N [0000-0002-9457-1941], Pober, JC [0000-0002-3492-0433], Williams, PKG [0000-0003-3734-3587], and Apollo - University of Cambridge Repository

Subjects
Physics, Cosmological evolution, Hydrogen, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, chemistry.chemical_element, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Cosmology, Data modeling, chemistry, Reionization, Space and Planetary Science, 0103 physical sciences, Radio interferometry, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

We analyze data from the Hydrogen Epoch of Reionization Array. This is the third in a series of papers on the closure phase delay-spectrum technique designed to detect the HI 21cm emission from cosmic reionization. We present the details of the data and models employed in the power spectral analysis, and discuss limitations to the process. We compare images and visibility spectra made with HERA data, to parallel quantities generated from sky models based on the GLEAM survey, incorporating the HERA telescope model. We find reasonable agreement between images made from HERA data, with those generated from the models, down to the confusion level. For the visibility spectra, there is broad agreement between model and data across the full band of $\sim 80$MHz. However, models with only GLEAM sources do not reproduce a roughly sinusoidal spectral structure at the tens of percent level seen in the observed visibility spectra on scales $\sim 10$ MHz on 29 m baselines. We find that this structure is likely due to diffuse Galactic emission, predominantly the Galactic plane, filling the far sidelobes of the antenna primary beam. We show that our current knowledge of the frequency dependence of the diffuse sky radio emission, and the primary beam at large zenith angles, is inadequate to provide an accurate reproduction of the diffuse structure in the models. We discuss implications due to this missing structure in the models, including calibration, and in the search for the HI 21cm signal, as well as possible mitigation techniques., Comment: 17 pages, 10 figures, accepted for the ApJ Supplement

Published
2020

17. Mitigating Internal Instrument Coupling for 21 cm Cosmology. II. A Method Demonstration with the Hydrogen Epoch of Reionization Array

Author

Nipanjana Patra, Ziyaad Halday, Adrian Liu, Matt Dexter, Joshua Kerrigan, Judd D. Bowman, Samantha Pieterse, Chris Carilli, David DeBoer, Eloy de Lera Acedo, Peter K. G. Williams, Zara Abdurashidova, Haoxuan Zheng, Piyanat Kittiwisit, Nithyanandan Thyagarajan, Kathryn Rosie, Austin Julius, Adam P. Beardsley, Philip Bull, David MacMahon, Adam Lanman, Jack Hickish, Gianni Bernardi, James Robnett, Angelo Syce, Jacob Burba, Bryna J. Hazelton, Deepthi Gorthi, Joshua S. Dillon, Richard F. Bradley, Matthew Kolopanis, Brian Glendenning, Matthys Maree, Paul Alexander, Carina Cheng, Miguel F. Morales, Mathakane Molewa, Zaki S. Ali, Bradley Greig, Craig Smith, Aaron Ewall-Wice, Saul A. Kohn, Telalo Lekalake, Nima Razavi-Ghods, Tshegofalang Mosiane, Jon Ringuette, Steve R. Furlanetto, Lourence Malan, Jacqueline N. Hewitt, Aaron R. Parsons, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, Nicholas S. Kern, Zachary E. Martinot, Paul La Plante, Steven G. Murray, Daniel C. Jacobs, Cresshim Malgas, Abraham R. Neben, Nicolas Fagnoni, Randall Fritz, Yanga Balfour, Eunice Matsetela, Peter Sims, James E. Aguirre, ITA, USA, ZAF, Kern, N. S., Parsons, A. R., Dillon, J. S., Lanman, A. E., Liu, A., Bull, P., Ewall-Wice, A., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Bernardi, G., Bowman, J. D., Bradley, R. F., Burba, J., Carilli, C. L., Chen, Cheng, Deboer, D. R., Dexter, M., De Lera Acedo, E., Fagnoni, N., Fritz, R., Furlanetto, S. R., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Julius, A., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., La Plante, P., Lekalake, T., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Murray, S. G., Neben, A. R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sims, P., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
Coupling, Physics, 010504 meteorology & atmospheric sciences, Dynamic range, Spectral density, Astronomy and Astrophysics, Astrophysics, HERA, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Signal, Noise floor, Cosmology, Settore FIS/05 - Astronomia e Astrofisica, Space and Planetary Science, 0103 physical sciences, 010303 astronomy & astrophysics, Reionization, 0105 earth and related environmental sciences
Abstract

We present a study of internal reflection and cross-coupling systematics in Phase I of the Hydrogen Epoch of Reionization Array (HERA). In a companion paper, we outlined the mathematical formalism for such systematics and presented algorithms for modeling and removing them from the data. In this work, we apply these techniques to data from HERA’s first observing season as a method demonstration. The data show evidence for systematics that, without removal, would hinder a detection of the 21 cm power spectrum for the targeted Epoch of Reionization (EoR) line-of-sight modes in the range 0.2 h -1 Mpc-1 < {k}\parallel < 0.5 h -1 Mpc-1. In particular, we find evidence for nonnegligible amounts of spectral structure in the raw autocorrelations that overlaps with the EoR window and is suggestive of complex instrumental effects. Through systematic modeling on a single night of data, we find we can recover these modes in the power spectrum down to the integrated noise floor, achieving a dynamic range in the EoR window of 106 in power (mK2 units) with respect to the bright galactic foreground signal. Future work with deeper integrations will help determine whether these systematics can continue to be mitigated down to EoR levels. For future observing seasons, HERA will have upgraded analog and digital hardware to better control these systematics in the field.

Published
2020

18. Optimizing sparse RFI prediction using deep learning

Author

Nithyanandan Thyagarajan, Adam Lanman, Kathryn Rosie, Angelo Syce, Gianni Bernardi, Deepthi Gorthi, Joshua S. Dillon, Peter Sims, Judd D. Bowman, Brian Glendenning, Carina Cheng, Samantha Pieterse, Craig Smith, Nicholas S. Kern, Eunice Matsetela, Joshua Kerrigan, Miguel F. Morales, Piyanat Kittiwisit, Mathakane Molewa, Zaki S. Ali, Paul Alexander, Tshegofalang Mosiane, Aaron Ewall-Wice, Daniel C. Jacobs, Jack Hickish, Haoxuan Zheng, David MacMahon, Telalo Lekalake, Matt Dexter, Cresshim Malgas, Nicolas Fagnoni, Jacob Burba, Yanga Balfour, Adam P. Beardsley, Bradley Greig, Abraham R. Neben, Steve R. Furlanetto, Matthys Maree, Julia Estrada, David DeBoer, Randall Fritz, James E. Aguirre, Nipanjana Patra, Peter K. G. Williams, Nima Razavi-Ghods, Ziyaad Halday, Richard F. Bradley, Matthew Kolopanis, Paul La Plante, Aaron R. Parsons, Lourence Malan, Adrian Liu, Zara Abdurashidova, Austin Julius, Eloy de Lera Acedo, Jon Ringuette, James Robnett, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, Saul A. Kohn, Chris Carilli, Zachary E. Martinot, Bryna J. Hazelton, USA, Kerrigan, J., la Plante, P., Kohn, S., Pober, J. C., Aguirre, J., Abdurashidova, Z., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Bernardi, G., Bowman, J. D., Bradley, R. F., Burba, J., Carilli, C. L., Cheng, C., Deboer, D. R., Dexter, M., de Lera Acedo, E., Dillon, J. S., Estrada, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Glendenning, B., Greig, B., Grobbelaar, J., Gorthi, D., Halday, Z., Hazelton, B. J., Hickish, J., Jacobs, D. C., Julius, A., Kern, N. S., Kittiwisit, P., Kolopanis, M., Lanman, A., Lekalake, T., Liu, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Neben, A. R., Parsons, A. R., Patra, N., Pieterse, S., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sims, P., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), FOS: Physical sciences, Context (language use), 02 engineering and technology, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, 01 natural sciences, Radio telescope, Settore FIS/05 - Astronomia e Astrofisica, 020204 information systems, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, data analysis [methods], 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Discrete mathematics, Physics, business.industry, Deep learning, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, HERA, interferometric [techniques], Amplitude, Space and Planetary Science, data analysis – Techniques: interferometric [Methods], astro-ph.CO, Artificial intelligence, Radio interferometer, Astrophysics - Instrumentation and Methods for Astrophysics, business, Astronomical and Space Sciences, Astrophysics - Cosmology and Nongalactic Astrophysics, astro-ph.IM
Abstract

Radio Frequency Interference (RFI) is an ever-present limiting factor among radio telescopes even in the most remote observing locations. When looking to retain the maximum amount of sensitivity and reduce contamination for Epoch of Reionization studies, the identification and removal of RFI is especially important. In addition to improved RFI identification, we must also take into account computational efficiency of the RFI-Identification algorithm as radio interferometer arrays such as the Hydrogen Epoch of Reionization Array grow larger in number of receivers. To address this, we present a Deep Fully Convolutional Neural Network (DFCN) that is comprehensive in its use of interferometric data, where both amplitude and phase information are used jointly for identifying RFI. We train the network using simulated HERA visibilities containing mock RFI, yielding a known "ground truth" dataset for evaluating the accuracy of various RFI algorithms. Evaluation of the DFCN model is performed on observations from the 67 dish build-out, HERA-67, and achieves a data throughput of 1.6$\times 10^{5}$ HERA time-ordered 1024 channeled visibilities per hour per GPU. We determine that relative to an amplitude only network including visibility phase adds important adjacent time-frequency context which increases discrimination between RFI and Non-RFI. The inclusion of phase when predicting achieves a Recall of 0.81, Precision of 0.58, and $F_{2}$ score of 0.75 as applied to our HERA-67 observations., Comment: 11 pages, 7 figures

Published
2019

19. Understanding the HERA Phase I receiver system with simulations and its impact on the detectability of the EoR delay power spectrum

Author

Richard F. Bradley, Matthew Kolopanis, Nithyanandan Thyagarajan, Adam Lanman, Lourence Malan, Saul A. Kohn, Alec Josaitis, Adrian Liu, Bryna J. Hazelton, Matt Dexter, Haoxuan Zheng, Piyanat Kittiwisit, Nicholas S. Kern, Kingsley Gale-Sides, Deepthi Gorthi, Joshua S. Dillon, Paul Alexander, Honggeun Kim, Craig Smith, Miguel F. Morales, Steve R. Furlanetto, Adam P. Beardsley, Mathakane Molewa, Zaki S. Ali, Bojan Nikolic, Aaron Ewall-Wice, Tshegofalang Mosiane, Phil Bull, Nipanjana Patra, Jacqueline N. Hewitt, Ziyaad Halday, Angelo Syce, Abraham R. Neben, Randall Fritz, Juan Mena Parra, Jack Hickish, Aaron R. Parsons, Joshua Kerrigan, Brian Glendenning, Carina Cheng, Paul La Plante, James Robnett, Jacob Burba, Chris Carilli, Eloy de Lera Acedo, Telalo Lekalake, Zara Abdurashidova, Kathryn Rosie, Gianni Bernardi, David MacMahon, Austin Julius, Daniel C. Jacobs, Nima Razavi-Ghods, Cresshim Malgas, Nicolas Fagnoni, Yanga Balfour, Matthys Maree, Peter Sims, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, Tashalee S. Billings, Zachary E. Martinot, Bradley Greig, James E. Aguirre, Peter K. G. Williams, Eunice Matsetela, Judd D. Bowman, Samantha Pieterse, David DeBoer, ITA, USA, GBR, Fagnoni, N., De Lera Acedo, E., Deboer, D. R., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Bernardi, G., Billings, T. S., Bowman, J. D., Bradley, R. F., Bull, P., Burba, J., Carilli, C. L., Cheng, C., Dexter, M., Dillon, J. S., Ewall-Wice, A., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Josaitis, A., Julius, A., Kern, N. S., Kerrigan, J., Kim, H., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., Plante, P. L., Lekalake, T., Liu, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mena Parra, J., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Neben, A. R., Nikolic, B., Parsons, A. R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Robnett, J., Rosie, K., Sims, P., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
interferometers [instrumentation], first stars, Phase (waves), FOS: Physical sciences, 02 engineering and technology, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, 01 natural sciences, law.invention, Radio telescope, Telescope, Optics, Settore FIS/05 - Astronomia e Astrofisica, law, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, dark ages, 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Spectral density, 020206 networking & telecommunications, Astronomy and Astrophysics, numerical [methods], telescopes, HERA, interferometric [techniques], interferometer [instrumentation], Transmission (telecommunications), Space and Planetary Science, reionization, dark ages, reionization, first star, Antenna (radio), Astrophysics - Instrumentation and Methods for Astrophysics, business, Astronomical and Space Sciences, astro-ph.IM
Abstract

The detection of the Epoch of Reionization (EoR) delay power spectrum using a "foreground avoidance method" highly depends on the instrument chromaticity. The systematic effects induced by the radio-telescope spread the foreground signal in the delay domain, which contaminates the EoR window theoretically observable. Applied to the Hydrogen Epoch of Reionization Array (HERA), this paper combines detailed electromagnetic and electrical simulations in order to model the chromatic effects of the instrument, and quantify its frequency and time responses. In particular, the effects of the analogue receiver, transmission cables, and mutual coupling are included. These simulations are able to accurately predict the intensity of the reflections occurring in the 150-m cable which links the antenna to the back-end. They also show that electromagnetic waves can propagate from one dish to another one through large sections of the array due to mutual coupling. The simulated system time response is attenuated by a factor $10^{4}$ after a characteristic delay which depends on the size of the array and on the antenna position. Ultimately, the system response is attenuated by a factor $10^{5}$ after 1400 ns because of the reflections in the cable, which corresponds to characterizable ${k_\parallel}$-modes above 0.7 $h\;\rm{Mpc}^{-1}$ at 150 MHz. Thus, this new study shows that the detection of the EoR signal with HERA Phase I will be more challenging than expected. On the other hand, it improves our understanding of the telescope, which is essential to mitigate the instrument chromaticity., Comment: 13 pages, 17 figures - Submitted to MNRAS - 2nd revision

Published
2019
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20. Mitigating Internal Instrument Coupling for 21 cm Cosmology I: Temporal and Spectral Modeling in Simulations

Author

Adam Lanman, Joshua S. Dillon, Aaron R. Parsons, Nicholas S. Kern, Eloy de Lera Acedo, and Nicolas Fagnoni

Subjects
Physics, COSMIC cancer database, Cosmology and Nongalactic Astrophysics (astro-ph.CO), 010504 meteorology & atmospheric sciences, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Signal, Signal chain, Cosmology, Interferometry, Space and Planetary Science, 0103 physical sciences, Antenna (radio), Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Phenomenology (particle physics), Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Cosmology and Nongalactic Astrophysics, 0105 earth and related environmental sciences
Abstract

We study the behavior of internal signal chain reflections and antenna cross coupling as systematics for 21 cm cosmological surveys. We outline the mathematics for how these systematics appear in interferometric visibilities and describe their phenomenology. We then describe techniques for modeling and removing these systematics without attenuating the 21 cm signal in the data. This has critical implications for low-frequency radio surveys aiming to characterize the 21cm signal from the Epoch of Reionization and Cosmic Dawn, as systematics can cause bright foreground emission to contaminate the EoR window and prohibit a robust detection. We also quantify the signal loss properties of the systematic modeling algorithms, and show that our techniques demonstrate resistance against EoR signal loss. In a companion paper, we demonstrate these methods on data from the Hydrogen Epoch of Reionization Array as a proof-of-concept., Comment: Accepted to ApJ

Published
2019
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21. Quantifying EoR delay spectrum contamination from diffuse radio emission

Author

Adam Lanman, Jonathan C. Pober, Nicholas S. Kern, David DeBoer, Eloy de Lera Acedo, and Nicolas Fagnoni

Subjects
Physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Signal, Galaxy, Spectral line, Optics, Space and Planetary Science, Frequency domain, Chromatic scale, Antenna (radio), Astrophysics - Instrumentation and Methods for Astrophysics, business, Visibility, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics
Abstract

The 21 cm hyperfine transition of neutral hydrogen offers a promising probe of the large scale structure of the universe before and during the Epoch of Reionization, when the first ionizing sources formed. Bright radio emission from foreground sources remains the biggest obstacle to detecting the faint 21 cm signal. However, the expected smoothness of foreground power leaves a clean window in Fourier space where the EoR signal can potentially be seen over thermal noise. Though the boundary of this window is well-defined in principle, spectral structure in foreground sources, instrumental chromaticity, and choice of spectral weighting in analysis all affect how much foreground power spills over into the EoR window. In this paper, we run a suite of numerical simulations of wide-field visibility measurements, with a variety of diffuse foreground models and instrument configurations, and measure the extent of contaminated Fourier modes in the EoR window using a delay-transform approach to estimating power spectra. We also test these effects with a model of the HERA antenna beam generated from electromagnetic simulations, to take into account further chromatic effects in the real instrument. We find that foreground power spillover is dominated by the so-called "pitchfork effect", in which diffuse foreground power is brightened near the horizon due to the shortening of baselines. As a result, the extent of contaminated modes in the EoR window is largely constant over time, except when the galaxy is near the pointing center., Comment: 16 pages, 13 figures

Published
2019
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22. Fundamental uncertainty levels of 21cm power spectra from a delay analysis

Author

Adam Lanman and Jonathan C. Pober

Subjects
Physics, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Spectral density, Estimator, FOS: Physical sciences, Astronomy and Astrophysics, Murchison Widefield Array, Variance (accounting), HERA, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Computational physics, Space and Planetary Science, 0103 physical sciences, Astronomical interferometer, Sample variance, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

Several experimental efforts are underway to measure the power spectrum of 21cm fluctuations from the Epoch of Reionization (EoR) using low-frequency radio interferometers. Experiments like the Hydrogen Epoch of Reionization Array (HERA) and Murchison Widefield Array Phase II (MWA) feature highly-redundant antenna layouts, building sensitivity through redundant measurements of the same angular Fourier modes, at the expense of diminished UV coverage. This strategy limits the numbers of independent samples of each power spectrum mode, thereby increasing the effect of sample variance on the final power spectrum uncertainty. To better quantify this effect, we measure the sample variance of a delay-transform based power spectrum estimator, using both analytic calculations and simulations of flat-spectrum EoR-like signals. We find that for the shortest baselines in HERA, the sample variance can reach as high as 20%, and up to 30% for the wider fields-of-view of the MWA. Combining estimates from all the baselines in a HERA- or MWA-like 37 element redundant hexagonal array can lower the variance to $1-3$% for some Fourier modes. These results have important implications for observing and analysis strategies, and suggest that sample variance can be non-negligible when constraining EoR model parameters from upcoming 21cm data., Comment: 15 pages, 11 figures

Published
2019
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23. Measuring HERA's Primary Beam in Situ: Methodology and First Results

Author

Richard F. Bradley, Matthew Kolopanis, Jonathan C. Pober, Andrei Mesinger, Daniel C. Jacobs, Bradley Greig, Jasper Grobbelaar, Cresshim Malgas, Craig Smith, Nicolas Fagnoni, Peter Sims, Yanga Balfour, Joshua Kerrigan, Angelo Syce, Tashalee S. Billings, Zachary E. Martinot, Piyanat Kittiwisit, Aaron R. Parsons, Chuneeta D. Nunhokee, Chris Carilli, Kingsley Gale-Sides, Nicholas S. Kern, Eloy de Lera Acedo, Peter K. G. Williams, Paul Alexander, Eunice Matsetela, Saul A. Kohn, Adam Lanman, Paul La Plante, David DeBoer, Nima Razavi-Ghods, David MacMahon, Bryna J. Hazelton, Nipanjana Patra, Adam P. Beardsley, Jon Ringuette, Matt Dexter, Ziyaad Halday, Deepthi Gorthi, Adrian Liu, Brian Glendenning, Nithyanandan Thyagarajan, Abraham R. Neben, Joshua S. Dillon, Gianni Bernardi, Zara Abdurashidova, Carina Cheng, Lourence Malan, Judd D. Bowman, Randall Fritz, Samantha Pieterse, Jacob Burba, Miguel F. Morales, Austin Julius, Zaki S. Ali, Bojan Nikolic, Aaron Ewall-Wice, James Robnett, Jacqueline N. Hewitt, James E. Aguirre, Kathryn Rosie, Steve R. Furlanetto, Mathakane Molewa, Haoxuan Zheng, Tshegofalang Mosiane, Matthys Maree, Telalo Lekalake, ITA, USA, CAF, Nunhokee, C. D., Parsons, A. R., Kern, N. S., Nikolic, B., Pober, J. C., Bernardi, G., Carilli, C. L., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Billings, T. S., Bowman, J. D., Bradley, R. F., Burba, J., Cheng, C., Deboer, D. R., Dexter, M., Acedo, E. D. L., Dillon, J. S., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Jacobs, D. C., Julius, A., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., Plante, P. L., Lekalake, T., Liu, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Neben, A. R., Patra, N., Pieterse, S., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sims, P., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
In situ, Physics, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, HERA, 01 natural sciences, Cosmology, Nuclear physics, Settore FIS/05 - Astronomia e Astrofisica, Space and Planetary Science, Primary (astronomy), 0103 physical sciences, H I line emission, Radio astronomy, Astrophysics - Instrumentation and Methods for Astrophysics, 010306 general physics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Beam (structure), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

The central challenge in 21~cm cosmology is isolating the cosmological signal from bright foregrounds. Many separation techniques rely on the accurate knowledge of the sky and the instrumental response, including the antenna primary beam. For drift-scan telescopes such as the Hydrogen Epoch of Reionization Array \citep[HERA, ][]{DeBoer2017} that do not move, primary beam characterization is particularly challenging because standard beam-calibration routines do not apply \citep{Cornwell2005} and current techniques require accurate source catalogs at the telescope resolution. We present an extension of the method from \citet{Pober2012} where they use beam symmetries to create a network of overlapping source tracks that break the degeneracy between source flux density and beam response and allow their simultaneous estimation. We fit the beam response of our instrument using early HERA observations and find that our results agree well with electromagnetic simulations down to a -20~dB level in power relative to peak gain for sources with high signal-to-noise ratio. In addition, we construct a source catalog with 90 sources down to a flux density of 1.4~Jy at 151~MHz., 22 pages, 22 figures, accepted for publication in ApJ

Published
2020

24. First Season MWA Phase II Epoch of Reionization Power Spectrum Results at Redshift 7

Author

Adam Lanman, J. L. B. Line, Cathryn M. Trott, Miguel F. Morales, Jonathan C. Pober, Christene Lynch, Bryna J. Hazelton, R. C. Joseph, R. Byrne, Judd D. Bowman, Daniel Jacobs, B. Pindor, Christopher H. Jordan, David L. Kaplan, A. P. Beardsley, D. Kenney, Tom Booler, Kenji Kubota, Melanie Johnston-Hollitt, S. S. Murray, Steven Tingay, T. M. O. Franzen, M. Wilensky, Andrew R. Williams, Chen Wu, Rachel L. Webster, S. Yoshiura, M. Walker, D. Pallot, Daniel A. Mitchell, G. Sleap, Qinghua Zheng, Keitaro Takahashi, David Emrich, L. Horsley, Kenji Hasegawa, Brian Crosse, K. Steele, J. Riding, B. McKinley, Ian Sullivan, Nichole Barry, Wenyang Li, R. B. Wayth, J. S. B. Wyithe, T. Kaneuji, and M. Rahimi

Subjects
Physics, 010504 meteorology & atmospheric sciences, Phase (waves), Spectral density, Astronomy and Astrophysics, Murchison Widefield Array, Astrophysics, Space (mathematics), 01 natural sciences, Redshift, Interferometry, Space and Planetary Science, 0103 physical sciences, Calibration, Sensitivity (control systems), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

The compact configuration of Phase II of the Murchison Widefield Array (MWA) consists of both a redundant subarray and pseudo-random baselines, offering unique opportunities to perform sky-model and redundant interferometric calibration. The highly redundant hexagonal cores give improved power spectrum sensitivity. In this paper, we present the analysis of nearly 40 hours of data targeting one of the MWA's EoR fields observed in 2016. We use both improved analysis techniques presented in Barry et al. (2019) as well as several additional techniques developed for this work, including data quality control methods and interferometric calibration approaches. We show the EoR power spectrum limits at redshift 6.5, 6.8 and 7.1 based on our deep analysis on this 40-hour data set. These limits span a range in $k$ space of $0.18$ $h$ $\mathrm{Mpc^{-1}}$ $

Published
2019

25. Comparing Redundant and Sky Model Based Interferometric Calibration: A First Look with Phase II of the MWA

Author

David Emrich, Nithyanandan Thyagarajan, Pietro Procopio, Cathryn M. Trott, Nichole Barry, Miguel F. Morales, Zaki S. Ali, Aaron Ewall-Wice, Mark Walker, Andrew Williams, Han-Seek Kim, Steven G. Murray, Christopher H. Jordan, Max Tegmark, Brian Crosse, K. Steele, Aaron R. Parsons, D. L. Kaplan, D. Pallot, R. Subrahmanian, R. C. Joseph, Masoud Rahimi, Melanie Johnston-Hollitt, Stuart Wyithe, L. Horsley, P. Carroll, D. Kenney, Bartosz Pindor, Randall B. Wayth, Piyanat Kittiwisit, J. Riding, Jonathan C. Pober, Shiv K. Sethi, R. Byrne, Ian Sullivan, Joshua S. Dillon, Rachel L. Webster, Jacqueline N. Hewitt, Daniel A. Mitchell, Frank H. Briggs, W. Li, Abraham R. Neben, Judd D. Bowman, J. L. B. Line, Thomas M. O. Franzen, N. Udaya Shankar, A. R. Offringa, Adam Lanman, Chen Wu, Adam P. Beardsley, Benjamin McKinley, Daniel C. Jacobs, Lu Feng, Bryna J. Hazelton, Steven Tingay, and S. Paul

Subjects
010308 nuclear & particles physics, Computer science, Calibration (statistics), FOS: Physical sciences, Spectral density, Astronomy and Astrophysics, Murchison Widefield Array, 01 natural sciences, Interferometry, Space and Planetary Science, 0103 physical sciences, Satellite, Deconvolution, Antenna (radio), Visibility, Baseline (configuration management), Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Algorithm
Abstract

Interferometric arrays seeking to measure the 21 cm signal from the Epoch of Reionization must contend with overwhelmingly bright emission from foreground sources. Accurate recovery of the 21 cm signal will require precise calibration of the array, and several new avenues for calibration have been pursued in recent years, including methods using redundancy in the antenna configuration. The newly upgraded Phase II of Murchison Widefield Array (MWA) is the first interferometer that has large numbers of redundant baselines while retaining good instantaneous UV-coverage. This array therefore provides a unique opportunity to compare redundant calibration with sky-model based algorithms. In this paper, we present the first results from comparing both calibration approaches with MWA Phase II observations. For redundant calibration, we use the package OMNICAL, and produce sky-based calibration solutions with the analysis package Fast Holographic Deconvolution (FHD). There are three principal results. (1) We report the success of OMNICAL on observations of ORBComm satellites, showing substantial agreement between redundant visibility measurements after calibration. (2) We directly compare OMNICAL calibration solutions with those from FHD, and demonstrate these two different calibration schemes give extremely similar results. (3) We explore improved calibration by combining OMNICAL and FHD. We evaluate these combined methods using power spectrum techniques developed for EoR analysis and find evidence for marginal improvements mitigating artifacts in the power spectrum. These results are likely limited by signal-to-noise in the six hours of data used, but suggest future directions for combining these two calibration schemes., 20 pages, 11 figures. Accepted to ApJ

Published
2018

26. Improved 21 cm Epoch Of Reionization Power Spectrum Measurements with a Hybrid Foreground Subtraction and Avoidance Technique

Author

Jonathan C. Pober, Aaron R. Parsons, Nichole Barry, Wenyang Li, Adrian Liu, Carina Cheng, Matthew Kolopanis, Ian Sullivan, James E. Aguirre, Joshua S. Dillon, Gianni Bernardi, Saul A. Kohn, Richard F. Bradley, Daniel C. Jacobs, Joshua Kerrigan, David DeBoer, Adam Lanman, Adam P. Beardsley, Chris Carilli, Zaki S. Ali, and USA

Subjects
Physics, Cosmology and Nongalactic Astrophysics (astro-ph.CO), 010308 nuclear & particles physics, Subtraction, Astrophysics::Instrumentation and Methods for Astrophysics, Spectral density, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Space and Planetary Science, Computer Science::Computer Vision and Pattern Recognition, 0103 physical sciences, Dark Ages, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Observations of the 21cm Epoch of Reionization (EoR) signal are dominated by Galactic and extragalactic foregrounds. The need for foreground removal has led to the development of two main techniques, often referred to as "foreground avoidance" and "foreground subtraction." Avoidance is associated with filtering foregrounds in Fourier space, while subtraction uses an explicit foreground model that is removed. Using 1088 hours of data from the 64-element PAPER array, we demonstrate that subtraction of a foreground model prior to delay-space foreground filtering results in a modest but measurable improvement of the performance of the filter. This proof-of-concept result shows that improvement stems from the reduced dynamic range requirements needed for the foreground filter: subtraction of a foreground model reduces the total foreground power, so for a fixed dynamic range, the filter can push towards fainter limits. We also find that the choice of window function used in the foreground filter can have an appreciable affect on the performance near the edges of the observing band. We demonstrate these effects using a smaller 3 hour sampling of data from the MWA, and find that the hybrid filtering and subtraction removal approach provides similar improvements across the band as seen in the case with PAPER-64., Comment: 20 pages, 12 figures

Published
2018
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27. pyuvsim: A comprehensive simulation package for radio interferometers in python

Author

Adam Lanman, Bryna J. Hazelton, Matthew Kolopanis, Nithyanandan Thyagarajan, Jonathan C. Pober, Daniel C. Jacobs, and James E. Aguirre

Subjects
Programming language, Computer science, Astronomical interferometer, Python (programming language), computer.software_genre, computer, computer.programming_language
Published
2019

28. Improved 21 cm Epoch of Reionization Power Spectrum Measurements with a Hybrid Foreground Subtraction and Avoidance Technique.

Author

Joshua R. Kerrigan, Jonathan C. Pober, Zaki S. Ali, Carina Cheng, Adam P. Beardsley, Aaron R. Parsons, James E. Aguirre, Nichole Barry, Richard F. Bradley, Gianni Bernardi, Chris L. Carilli, David R. DeBoer, Joshua S. Dillon, Daniel C. Jacobs, Saul A. Kohn, Matthew Kolopanis, Adam Lanman, Wenyang Li, Adrian Liu, and Ian Sullivan

Subjects
IONIZATION (Atomic physics), GALACTIC coordinates, SAMPLING (Process), FOURIER analysis
Abstract

Observations of the 21 cm Epoch of Reionization signal are dominated by Galactic and extragalactic foregrounds. The need for foreground removal has led to the development of two main techniques, often referred to as “foreground avoidance” and “foreground subtraction.” Avoidance is associated with filtering foregrounds in Fourier space, while subtraction uses an explicit foreground model that is removed. Using 1088 hr of data from the 64-element PAPER array, we demonstrate that subtraction of a foreground model prior to delay-space foreground filtering results in a modest but measurable improvement of the performance of the filter. This proof-of-concept result shows that improvement stems from the reduced dynamic range requirements needed for the foreground filter: subtraction of a foreground model reduces the total foreground power, so for a fixed dynamic range, the filter can push toward fainter limits. We also find that the choice of window function used in the foreground filter can have an appreciable affect on the performance near the edges of the observing band. We demonstrate these effects using a smaller 3 hr sampling of data from the MWA, and find that the hybrid filtering and subtraction removal approach provides similar improvements across the band as seen in the case with PAPER-64. [ABSTRACT FROM AUTHOR]

Published
2018
Full Text
View/download PDF

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